U.S. Pat. No. 4,975,354 issued Dec. 4, 1990, entitled "Photographic Element Comprising An Ethyleneoxy-Substituted Amino Compound And Process Adapted To Provide High Contrast Development", by Harold I. Machonkin and Donald L. Kerr, describes silver halide photographic elements having incorporated therein a hydrazine compound which functions as a nucleator and an amino compound which functions as an incorporated booster. Such elements provide a highly desirable combination of high photographic speed, very high contrast and excellent dot quality, which renders them very useful in the field of graphic arts. Moreover, since they incorporate the booster in the photographic element, rather than using a developing solution containing a booster, they have the further advantage that they are processable in conventional, low cost, rapid-access developers.
Photographic elements of the type described in the aforesaid U.S. Pat. No. 4,975,354 are critically dependent on the use of sensitizing dyes. Silver halide crystals, such as silver chloride, silver bromide, silver iodide, silver chlorobromide and silver bromoiodide, absorb light in the ultraviolet and blue regions of the spectrum to form latent images that can be amplified by chemical development. To make the silver halide grains sensitive to wavelengths in other regions of the electromagnetic spectrum, it is well known to add spectral sensitizing dyes to the silver halide emulsion. These dyes are adsorbed to the surface of the silver halide crystals and must be efficient at absorbing incident light and transferring the energy to the silver halide. Furthermore, since these dyes do not form part of the final image, it is desirable that they be decolorized or removed from the photographic element during processing to avoid objectionable sensitizing dye stain.
Dye stain is a matter of particularly great concern with photographic elements used in the graphic arts industry. These photographic elements are processed to produce black-and-white images that are very high in contrast. Retained sensitizing dye causes discoloration of the white areas, and degrades the appearance and performance of the photographic elements.
In the graphic arts industry, it is also very important that photographic elements can be processed rapidly in order to provide enhanced efficiency and productivity. The use of very short development times, such as times of thirty to forty seconds or less, is commonly referred to in the trade as "rapid access processing". Elements which are capable of rapid access processing can be most easily achieved through the use of high-chloride emulsions, because such emulsions exhibit enhanced developability relative to bromide or iodide emulsions. However, efficient spectral sensitization of high-chloride emulsions is very difficult to achieve. Adsorption of spectral sensitizing dyes generally increases in the order silver chloride&lt;silver bromide&lt;silver iodide. Poor adsorption of sensitizing dye leads to loss of photographic speed. Dyes which are strongly adsorbed to silver chloride, on the other hand, frequently can not be removed during rapid processing, and cause objectionable levels of sensitizing dye stain. Accordingly, to achieve the advantages inherent in the use of high-chloride emulsions in photographic elements of the type described in U.S. Pat. No. 4,975,354, it is critically important to utilize a sensitizing dye meeting the dual objectives of excellent sensitizing capability with minimal tendency to cause stain.
It is toward the objective of providing improved nucleated, high-contrast, high-chloride photographic elements containing spectral sensitizing dyes that provide improved photographic sensitivity--yet leave substantially no sensitizing dye stain after rapid access processing--that the present invention is directed.